Effectiveness of Hepatitis B Treatment in Clinical Practice

Scaglione, Steven; Lok, Anna S.

doi:10.1053/j.gastro.2012.01.044

Cited by 125 publications

(131 citation statements)

References 67 publications

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“…Based on differential sequence and structural requirements defined using the duck hepatitis B virus (DHBV) polymerase, protein priming can be divided into two distinct stages, the initial attachment of the first dGMP residue to the polymerase (initiation or polymerase deoxyguanidinylation) followed by the addition of two (dAA; for HP) or three (dTAA; for the DHBV polymerase) nucleotide residues to the initiating dGMP (DNA polymerization) (7,19,20). After protein priming, the nascent minusstrand-HP complex is transferred from the Hε template to a complementary sequence at the 3= end of pgRNA called DR1, where HP continues minus-strand DNA elongation (7,10,21).Current treatments for chronic HBV infection include pegylated alpha interferon and nucleos(t)ide RT inhibitors (NRTIs) (22,23). Interferon therapy is effective only in a minority of patients and is associated with side effects and toxicities.…”

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confidence: 99%

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Noncompetitive Inhibition of Hepatitis B Virus Reverse Transcriptase Protein Priming and DNA Synthesis by the Nucleoside Analog Clevudine

Jones

Murakami

Delaney

et al. 2013

Antimicrob Agents Chemother

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c All currently approved antiviral drugs for the treatment of chronic hepatitis B virus (HBV) infection are nucleos(t)ide reverse transcriptase inhibitors (NRTI), which inhibit the DNA synthesis activity of the HBV polymerase. The polymerase is a unique reverse transcriptase (RT) that has a novel protein priming activity in which HP initiates viral DNA synthesis using itself as a protein primer. We have determined the ability of NRTI-triphosphates (TP) to inhibit HBV protein priming and their mechanisms of action. While entecavir-TP (a dGTP analog) inhibited protein priming initiated specifically with dGTP, clevudine-TP (a TTP analog) was able to inhibit protein priming independently of the deoxynucleoside triphosphate (dNTP) substrate and without being incorporated into DNA. We next investigated the effect of NRTIs on the second stage of protein priming, wherein two dAMP nucleotides are added to the initial deoxyguanosine nucleotide. The obtained results indicated that clevudine-TP as well as tenofovir DF-DP strongly inhibited the second stage of protein priming. Tenofovir DF-DP was incorporated into the viral DNA primer, whereas clevudine-TP inhibited the second stage of priming without being incorporated. Finally, kinetic analyses using the HBV endogenous polymerase assay revealed that clevudine-TP inhibited DNA chain elongation by HP in a noncompetitive manner. Thus, clevudine-TP appears to have the unique ability to inhibit HBV RT via binding to and distorting the HP active site, sharing properties with both NRTIs and nonnucleoside RT inhibitors. C hronic hepatitis B virus (HBV) infection remains a worldwide health problem, afflicting over 350 million patients and resulting in one million deaths per year (1). HBV has a ca. 3.2-kb relaxed circular (RC) DNA genome that is repaired to form a covalently closed circular (CCC) DNA in the host cell. CCC DNA is then transcribed by the host RNA polymerase II to produce a pregenomic RNA (pgRNA), the precursor to RC DNA (2, 3). Reverse transcription of pgRNA by the viral polymerase (HP), a multifunctional reverse transcriptase (RT), generates first the minus strand and then the plus strand of RC DNA using its RNA-and DNA-dependent DNA polymerization activities, respectively (2, 4).Initiation of viral minus-strand DNA synthesis occurs via a novel protein priming mechanism in which HP, specifically a tyrosine residue (Y63) in its N-terminal domain, serves as a protein primer, while its central RT domain serves as the catalyst (5-9). Furthermore, protein-primed initiation of reverse transcription requires a short RNA stem-loop structure, termed epsilon (Hε), on the 5= end of pgRNA, which is recognized specifically by HP in a host chaperone-dependent reaction (7, 10-15). Hε, specifically the last three nucleotides of its internal bulge, serves as the specific template for protein priming (7,10,16). Furthermore, it serves as an allosteric activator of the HP enzymatic activity (17, 18). The product of protein priming is a short, 3-nucleotide (nt)-long (dGAA) viral minus-st...

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confidence: 99%

“…Current treatments for chronic HBV infection include pegylated alpha interferon and nucleos(t)ide RT inhibitors (NRTIs) (22,23). Interferon therapy is effective only in a minority of patients and is associated with side effects and toxicities.…”

mentioning

confidence: 99%

Noncompetitive Inhibition of Hepatitis B Virus Reverse Transcriptase Protein Priming and DNA Synthesis by the Nucleoside Analog Clevudine

Jones

Murakami

Delaney

et al. 2013

Antimicrob Agents Chemother

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“…These processes may be related to the pathogenesis of the inflammatory diseases associated with HBVinduced hepatitis, leading ultimately to cirrhosis and HCC. Indeed, HBV RT inhibitors (nucleoside analogues, such as ETV, used here) are highly effective in suppressing the necroinflammatory process in the HBV-infected liver, slowing/reversing cirrhosis and delaying/preventing HCC (48,63,64). This anti-inflammatory effect is observed despite the fact that RT inhibitors have no direct effect on viral gene expression but instead only block viral DNA synthesis.…”

Section: Discussionmentioning

confidence: 98%

Viral DNA-Dependent Induction of Innate Immune Response to Hepatitis B Virus in Immortalized Mouse Hepatocytes

Cui

Clark

Liu

et al. 2016

J Virol

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Hepatitis B virus (HBV) infects hundreds of millions of people worldwide and causes acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HBV is an enveloped virus with a relaxed circular (RC) DNA genome. In the nuclei of infected human hepatocytes, conversion of RC DNA from the incoming virion or cytoplasmic mature nucleocapsid (NC) to the covalently closed circular (CCC) DNA, which serves as the template for producing all viral transcripts, is essential to establish and sustain viral replication. A prerequisite for CCC DNA formation is the uncoating (disassembly) of NCs to expose their RC DNA content for conversion to CCC DNA. We report here that in an immortalized mouse hepatocyte cell line, AML12HBV10, in which RC DNA exposure is enhanced, the exposed viral DNA could trigger an innate immune response that was able to modulate viral gene expression and replication. When viral gene expression and replication were low, the innate response initially stimulated these processes but subsequently acted to shut off viral gene expression and replication after they reached peak levels. Inhibition of viral DNA synthesis or cellular DNA sensing and innate immune signaling diminished the innate response. These results indicate that HBV DNA, when exposed in the host cell cytoplasm, can function to trigger an innate immune response that, in turn, modulates viral gene expression and replication. IMPORTANCE Chronic infection by hepatitis B virus (HBV) afflicts hundreds of millions worldwide and is sustained by the episomal covalently closed circular (CCC) DNA in the nuclei of infected hepatocytes.Release of viral genomic DNA from cytoplasmic nucleocapsids (NCs) (NC disassembly or uncoating) is a prerequisite for its conversion to CCC DNA, which can also potentially expose the viral DNA to host DNA sensors and trigger an innate immune response. We have found that in an immortalized mouse hepatocyte cell line in which efficient CCC DNA formation was associated with enhanced exposure of nucleocapsid-associated DNA, the exposed viral DNA indeed triggered host cytoplasmic DNA sensing and an innate immune response that was able to modulate HBV gene expression and replication. Thus, HBV can, under select conditions, be recognized by the host innate immune response through exposed viral DNA, which may be exploited therapeutically to clear viral persistence. Hepatitis B virus (HBV) has infected approximately 2 billion people worldwide, with 350 million of them becoming chronically infected (1). Annually, 1 million fatalities are attributed to acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC) caused by HBV. HBV is a small, enveloped DNA virus that contains a 3.2-kb, partially double-stranded (DS), relaxed circular (RC) DNA genome and replicates via an RNA intermediate, the pregenomic RNA (pgRNA). Upon infection, HBV RC DNA is converted to covalently closed circular (CCC) DNA in the nuclei of infected human hepatocytes, which serves as the transcriptional template for all viral RNAs, incl...

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“…Current treatments with IFN-α or nucleos(t)ide analogs (NAs) are only partially effective (3,4). Importantly, they do not directly target the viral persistence reservoir, an episomal covalently closed circular (ccc) DNA form of the viral genome that serves as template for all viral transcripts; hence a few cccDNA molecules present in the liver can reactivate full viral replication.…”

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confidence: 99%

Involvement of the host DNA-repair enzyme TDP2 in formation of the covalently closed circular DNA persistence reservoir of hepatitis B viruses

Königer

Wingert

Marsmann

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

206

193

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Hepatitis B virus (HBV), the causative agent of chronic hepatitis B and prototypic hepadnavirus, is a small DNA virus that replicates by protein-primed reverse transcription. The product is a 3-kb relaxed circular DNA (RC-DNA) in which one strand is linked to the viral polymerase (P protein) through a tyrosyl-DNA phosphodiester bond. Upon infection, the incoming RC-DNA is converted into covalently closed circular (ccc) DNA, which serves as a viral persistence reservoir that is refractory to current anti-HBV treatments. The mechanism of cccDNA formation is unknown, but the release of P protein is one mandatory step. Structural similarities between RC-DNA and cellular topoisomerase-DNA adducts and their known repair by tyrosyl-DNA-phosphodiesterase (TDP) 1 or TDP2 suggested that HBV may usurp these enzymes for its own purpose. Here we demonstrate that human and chicken TDP2, but only the yeast ortholog of TDP1, can specifically cleave the Tyr-DNA bond in virus-adapted model substrates and release P protein from authentic HBV and duck HBV (DHBV) RC-DNA in vitro, without prior proteolysis of the large P proteins. Consistent with TPD2's having a physiological role in cccDNA formation, RNAi-mediated TDP2 depletion in human cells significantly slowed the conversion of RC-DNA to cccDNA. Ectopic TDP2 expression in the same cells restored faster conversion kinetics. These data strongly suggest that TDP2 is a first, although likely not the only, host DNA-repair factor involved in HBV cccDNA biogenesis. In addition to establishing a functional link between hepadnaviruses and DNA repair, our results open new prospects for directly targeting HBV persistence.hepatitis B virus persistence | TDP substrate specificity | virus-DNA repair interface M ore than 250 million people worldwide are chronically infected with hepatitis B virus (HBV) (1) and are at a highly increased risk for developing end-stage liver disease (2). Current treatments with IFN-α or nucleos(t)ide analogs (NAs) are only partially effective (3, 4). Importantly, they do not directly target the viral persistence reservoir, an episomal covalently closed circular (ccc) DNA form of the viral genome that serves as template for all viral transcripts; hence a few cccDNA molecules present in the liver can reactivate full viral replication. Eliminating infection thus will require the elimination of cccDNA. cccDNA is generated, upon infection, from the viral polymerase (P protein)-linked relaxed circular (RC) DNA present in incoming virions (Fig. 1A). The mechanism by which RC-DNA is converted to cccDNA is poorly understood, but it must involve multiple steps (see below). Because the ∼3-kb genomes of HBV and the other hepadnaviruses [e.g., from ducks (DHBV)] are too small to encode all the activities required for this conversion, these activities must be provided by the host cell.RC-DNA from all hepadnaviruses bears several molecular peculiarities that result from its generation by protein-primed reverse transcription (for reviews, see refs. 5 and 6). The pregenomic RNA (p...

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Effectiveness of Hepatitis B Treatment in Clinical Practice

Cited by 125 publications

References 67 publications

Noncompetitive Inhibition of Hepatitis B Virus Reverse Transcriptase Protein Priming and DNA Synthesis by the Nucleoside Analog Clevudine

Noncompetitive Inhibition of Hepatitis B Virus Reverse Transcriptase Protein Priming and DNA Synthesis by the Nucleoside Analog Clevudine

Viral DNA-Dependent Induction of Innate Immune Response to Hepatitis B Virus in Immortalized Mouse Hepatocytes

Involvement of the host DNA-repair enzyme TDP2 in formation of the covalently closed circular DNA persistence reservoir of hepatitis B viruses

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